Thermoplastic draw tape or strip bags are widely known. Such bags are formed from superposed thermoplastic panels typically heat sealed along their bottom or two side edges in having an open side or mouth bordered by a sealed tube. The tube is formed by turning over or hemming the panel material and sealing the edge of the turned portion of the material to the opposed connected portion of the panel to form the tunnel structure. The tunnel structure of each panel typically contains a separate draw strip. Openings through the tunnel structure on either side of the mouth allow access to the strip therein which, when drawn through the opening, cinches the bag mouth closed and provides handles for carrying the bag.
A number of patents, particularly U.S. Pat. Nos. 2,777,491, 2,897,729, and 3,512,456, depict the manufacture of draw string bags by outwardly hemming (i.e., outwardly turning) the adjoining free edges of a once folded plastifilm web and inserting strings into the folds of the hem from a position opposite the fold. This method produces an exposed, hemmed edge on the outer surface of the bag which is not aesthetically pleasing.
The method typically employed to make draw tape bags with inwardly folded hems is shown in U.S. Pat. Nos. 2,798,523, 3,196,757, 3,738,567 and 3,772,968 and consists of applying the tape strips near either side edge of an unfolded plastifilm web, folding the edges towards one another over the strips to form a pair of hemmed tunnels containing the strips and then centralling folding the web with the turned in hems facing one another. All this produces a satisfactory product, a great deal of floor space must be provided in manufacture so as to be able to deal with the originally unfolded web.
In the manufacture of other types of bags, a pliable strip is sometimes inserted into the fold of a once folded web from a position outside and opposite to the fold. In particular, U.S. Pat. No. 3,803,990 describes the used of guide member extending transversely between the panels of a once folded continuous web to a position near the fold. A continuous strip of pliable material is fed along the guide to a turning edge oriented at 45.degree. to the longitudinally direction of the web and transverse direction of the guide and turned over the edge so as extend longitudinally, i.e., parallel to the fold. U.S. Pat. No. 3,687,357 depicts the fabrication of draw string bags in which a pair of strings are fed into either outwardly turned or inwardly turned hemmed edges of a continuous plastifilm web. The actual insertion device used is only diagrammatically depicted and is not otherwise described.